To produce bitumen, two processes are used continuously and continuously, each of which is as follows:
Batch Process
In this process, the aerated tower is filled with a certain volume of feed and after blowing air with pre-conditioned conditions. Determined (reaction temperature, feed time and amount) and the product reaches the desired specifications, the tower is emptied and its contents are entered into the tanks.
The main components of the aeration unit
in a batch process aeration main components are:
-Kvrh pre-heater Pre Heater
-Dmndh Blower or Compressor air compressor
-Brj aerated Oxidizer Tower
-Air for collecting and burning fumes
Continuous process
In this process, feed enters the aeration tower continuously with a certain amount and can be controlled with a predetermined temperature, and after performing aeration operations in constant operating conditions, it leaves the aeration tower. This method of preparing bitumen, which is used in refineries, is considered due to the following advantages.
-Reduction of pollutant vapors.
-Reduction of equipment and maintenance costs.
-Increasing the efficiency and amount of production per unit time.
- Reduce the thermal load of food preheaters.
- Ease of control and process operations due to its continuous nature.
- Less air consumption and shorter aeration time due to the optimal use of blown air.
It should be noted that aeration is possible in horizontal and vertical towers, but due to the higher efficiency of vertical towers, they are preferred.
Effective parameters in aeration
In aeration, several parameters are important, the most important of which are:
-Food oxidation
-feed food
The geometric shape of the tower
During the aeration process by oxidation, air passes through the bitumen and its oxygen interacts with the bitumen molecules. The vapors from this process (Process Fumes) contain less than 10% oxygen and various compounds such as water vapor, aldehydes, ketones, Co, Co2, nitrogen oxides, methane, sulfur compounds (SO2, H2S) and finally "hydrocarbons". "Oil is oil." These hydrocarbons are removed from the tower by intense air flow, either in the form of vapor or liquid with air, and some of them are stored in subsequent stages (Condense). These hydrocarbons are called "process oils" and the vapors of this aeration process are usually treated by a set of detachable devices rather than accompanying oils (or later). Condensed) are separated and then the vapors are burned.The rate of feed loss in the aeration process usually varies between (0.5-2)% by weight, this rate depends on several factors such as feed viscosity, temperature, aeration time and .... Most of the process vapors include this loss. A partial Knok Out Drum or Vapor Trap is required to partially degrease the exhaust gases. In some cases, Knok Out Drum is equipped with a water spray that will cause more lubrication, which is known as Contact Condenser. In other cases, methods such as returning vapors to the blower are used. Alternatively, when there is enough space, use the following simple system: The vapors pass through a horizontal and longitudinal air condenser (heat exchanger), separating most of the accompanying oils, and the remaining vapors burning to one. The vertical furnace is guided.At the end of this article, it is necessary to explain that bitumen feed is the residue of the vacuum distillation tower (Vacumbottom) which is produced in the distillation unit and flows to the aeration tower and the air required for oxidation is supplied by the blower and compressor. It is provided through the service unit (Utility). After aeration, bitumen is removed from the tower at a temperature of about C0 250 to 260 C0 and cooled by three heat exchangers and directed to the storage tanks of the product. The temperature of these tanks is kept at C0 188, which is sampled by filling each of the tanks and sent to the loading tanks after confirming the quality control of the laboratory. To prevent environmental pollution, light gases emitted from the top of the reaction tower caused by dehydrogenation after entering the Knock Out Drum and settling heavy liquids are directed to the incinerator furnace and burned with natural gas at a temperature of C0 800 Be.
Process variables:
Two influential variables on blown bitumen are feed composition and aeration time. Other variables include temperature, aeration intensity and bitumen height. Reducing the residence time of bitumen in the tower is generally economical at constant temperature and aeration time. The process is usually performed at atmospheric pressure. The design of the tower and the method of operation also affect the properties of the product because it affects the amount of oil lost.
A) Food:
The specifications of the feed and the desired product are determined through feed experiments, market needs determination and bitumen specifications required for mixing with soft bitumen in insulation or asphalt units and so on. The feed of most aeration units in Iran is bitumen 60/70 refinery. You can see the 60/70 bitumen analysis on the bitumen analysis page offered by Fidar TABRIZ - SANA, Company .
B) Temperature:
After determining the feed and product specifications, the aeration temperature is determined. Temperature has the following effects:
1) The type and speed of the chemical reaction that changes the quality of the product
2) Bitumen dehydration, which is a determining factor in oxygen consumption.
The quality of blown bitumen improves with decreasing temperature. Bitumen blown at high temperatures has a lower penetration rate. When determining the process temperature, considerations must be taken into account the maximum allowable amount of oxygen in the exhaust gases and the relationship between production costs and product quality.
C) Dimensions of aeration containers:
The intensity of aeration temperature and liquid height are determined according to the dimensions and capacity of aeration vessels. Advanced towers are generally 6 meters high. Of course, towers with a height of 7.5 to 11 meters have also been built, which has yielded good results.
D) Height of liquid:
Low bitumen height with high oxygen concentration causes explosion. High altitude may also lead to bitumen overflow into the gas outlet system or outlet through the release tool. Reading the temperature with a variety of devices and at different heights can show problems in the height of the bitumen or the presence of too much foam. The usual temperature difference between the high level of bitumen and the vapors of the outlet is between 25 and 35 degrees Celsius.
Operation problems
1) Freckles:
The high temperature of the fire hoses as well as the cooling of the exhaust vapors at the top of the tower lead to the production of fleas, which can enter the pump and damage it. To prevent this, it is better to use coking nets on the way out of the bitumen tower.
2) Cooling of the pipeline and blocking it:
In intermittent operations where there is a time interval between two loads, this causes the pipeline to be blocked. To solve this problem, it is recommended to install a small pipeline containing hot oil or steam in the vicinity of the pipes, because using fire with wood and diesel or torch to heat the pipes in addition to destroying pipes and valves pollutes the environment.
3) Final return:
If the product is blown in large quantities and does not cool immediately after aeration, the process of depilation or thermal cracking occurs, which is called the final return. As a result, the bitumen softens and its permeability increases. Final return is a common problem in disconnected units, which is controlled by a sudden cooling of the product (about 20. C).
4) Explosion of gases and vapors:
To prevent this problem, the intensity of aeration and the height of the bitumen inside the tower must be controlled. In large towers, a rapper disc is installed at the top of the tower to prevent damage from the explosion and a sudden increase in pressure. Another way is to return the vapors to the blower. Another system involves passing the output vapors into a horizontal, long air condenser and then sending it to the chimney. This traps the accompanying oils and dilutes the evaporator material better.
Factors affecting bitumen production:
1) By increasing the amount of injected air and temperature, the reaction rate increases
2) Increasing the stopping time of bitumen inside the tower increases Soft or bitumen softness.
3) The reaction starts at 420 degrees Fahrenheit and increases rapidly at 550 degrees Fahrenheit. The reaction takes place at 400 degrees Fahrenheit and below.
4) By keeping the temperature change ratio constant, increasing the aeration ratio increases the temperature and vice versa.
5) Thermal reaction can be controlled by Cold Recycle.
6) If the height of the liquid surface is low, it is not recommended to reduce the stopping time, because due to the contact of the hot liquid and the extra air coming out of the liquid molecules, it will lead to a fire.
7) The higher the difference between temperature (Point 1) and temperature (Base), the better the oxidation and reduction reaction.
8) In order to prevent fire at the top of the Snuffing Steam tower, it is injected into the tower.
9) The water pipe connected to the tower, which is used for washing during major repairs, must be blanked when the tower is active.
10) At the top of the tower, in addition to the Vapor Line, there is another 16-inch tube under which there is a Rupture Disc or tower safety valve. It drains the contents of the tower into the pool. If this happens, you must close the device and replace the Disc again.
Export bitumen
Bitumen
bitumen is a black, pasty material used to insulate moisture and make asphalt. There are many types of bitumen, each of which has its own uses. Bitumen is a derivative of oil.
Bitumen is a hydrocarbon substance in black to dark brown that dissolves completely in carbon sulfide and carbon tetrachloride. Bitumen is solid at room temperature. But with increasing temperature, it becomes a paste and then becomes liquid. The important use of bitumen is due to the presence of two important properties of this material;
* Water impermeability
* Adhesion
Bitumen is usually obtained by distilling crude oil. Such bitumen is called petroleum bitumen or distillation bitumen. Petroleum bitumen is the product of two stages of crude oil distillation in the distillation tower. In the first stage of distillation, light materials such as gasoline and propane are separated from the crude oil. This process is done at a pressure close to one atmosphere (unit). In the second stage, heavy compounds such as diesel and kerosene are removed. This process takes place at a pressure close to the vacuum. Eventually a mixture of very fine solid particles called asphaltene remains, which is immersed in a granular fluid called malt.
However, some types of bitumen are obtained in nature as a result of the gradual conversion of crude oil and the evaporation of its volatile substances over many years. Such bitumen is called natural bitumen and is more durable than petroleum bitumen. Such bitumen may be present in its pure form in nature (lake bitumen), such as Iran's Behbahan bitumen lake and Tirinidad bitumen lake in the United States, or extracted from mines.
Petroleum bitumens are petroleum
bitumens, solid and semi-solid bitumens that are obtained directly from the distillation of crude oil or by additional operations such as blowing air. Oil bitumen is a heavy residual or distilled crude oil distillate. Crude oil bitumen varies from zero to more than half. In addition, the bitumen obtained from different sources can have many differences. Therefore, bitumen refineries must carefully select their crude oil to ensure the quality of the bitumen.
Direct extraction of bitumen from crude oil
distillation is a fundamental process in crude oil refining. The first stage of distillation is done under atmospheric pressure and usually involves heating the crude oil to a temperature of about 650 to 800 degrees Fahrenheit and then injecting it into a separation column. In this way, the lighter cuts are called the top product of the tower and the bitumen residue is called the atmospheric residue. This is the first step in the whole treatment process. Many crude oils contain high percentages of high-boiling cuts that cannot be distilled in an atmospheric distillation unit. To separate these cuts and provide bitumen with the desired characteristics, a secondary separation tower that works in vacuum conditions is used.
The rest of this process is called direct extraction bitumen. The process of producing asphalt by vacuum distillation, except for permeability, has very little effect on the other properties of bitumen. The origin of the used crude oil also has a significant effect on the physical properties of the extracted bitumen.
Bitumen Specifications
1. Infiltration: The penetration test is used to determine the hardness of bitumen. In this experiment, a standard needle is penetrated into the bitumen at 25. C for 5 seconds under a 100 g load. The amount of penetration in tenths of a millimeter is called the degree of penetration. The lower the degree of penetration, the harder the bitumen.
2 - Aggregation: The slower the bitumen, the more solid properties it shows. It is clear that at higher temperatures the mental slowness is lower. This characteristic of bitumen is measured by a C-bolt Fiorel device or by kinematic method.
3. Ignition Degree: The degree of ignition is the temperature at which, if the bitumen reaches that temperature, the gases emitted by it will ignite as the flame approaches and a flame will form on its surface. The maximum temperature at which bitumen can be heated in the workshop is limited to the degree of ignition.
4. Weight loss: The weight loss of bitumen at high temperatures is due to the evaporation of some of its oils and petroleum compounds. This feature is also an important property of bitumen. The weight loss of bitumen in Owen is measured at 163. C for 5 hours (approximate asphalt cooking conditions).
5 - Formability or stigma: If we draw a sample of bitumen with a cross section of 1 cm square at a speed of 5 cm / min, the amount of increase in the length of the sample before the rupture of the bitumen property is called rupture.
6- Pure purity: We know that the solvent of tetra bitumen is carbon chloride and carbon sulfur. Therefore, if we dissolve a sample of bitumen in each of these materials, its impurities remain and from there we can determine the degree of purity of the bitumen. The degree of purity is: (bitumen sample weight) ÷ [(gross weight) - (bitumen weight)]
7 - Softness degree: The degree of softness is the temperature at which the bitumen reaches the temperature, the bitumen changes from solid to smooth. The higher the degree of softness of the bitumen, the less sensitive it is to temperature changes. The softness of ordinary bitumen is about 60 to 70.
Types of petroleum bitumen:
50-40
bitumen is a type of bitumen that is obtained in the oxidation process of vacuum baton and has a degree of penetration between 50-40.
Bitumen specifications 50-40 are given in the table below.
Bitumen 70-60
This bitumen has a degree of penetration between 70-60, the specifications of bitumen 70-60 are given in the table below.
Bitumen 100-85
This bitumen has a degree of penetration between 100-85, the specifications of bitumen 100-85 are given in the table below.
Consumption of bitumen
Important use of bitumen is due to the presence of two important properties of this material: impermeability to water and high adhesion due to these properties, the main use of bitumen in road construction and insulation.
The most important products produced from petroleum
bitumen:
Emulsion bitumen : Emulsion bitumen is produced in two types of anion and cation. Technically, the cations of cationic emulsions became popular from 1951 onwards, and due to their properties, they quickly replaced the bitumen of anionic emulsions. Water and bitumen do not mix together, but emulsion bitumen technology has made it possible to disperse a significant percentage of bitumen in the continuous water phase. A compound called emulsifier keeps bitumen particles suspended (with an electric charge) in a continuous phase of suspended and stable water.
In this mixture, bitumen (which should only be 50-40, 70-60 or 100-85 industrial bitumen) is not dissolved in water but floats in the water in the form of very small blood cells. In some cases, a stabilizer may be used in combination with emulsifiers. Emulsion bitumens are mainly liquid liquid emulsions in which the bitumen is dispersed in the water phase. In this type of bitumen emulsion, the amount of bitumen depends on its application, which usually varies from a minimum of 52% to a maximum of 69%.
Bitumen emulsions are broken down into three categories in terms of rate of breakdown (RS), slow breaker (MS) and late breaker (SS) and in terms of electroelectricity of bitumen suspended particles into three types: cationic (C), anionic (A) and amphoteric or neutral. Are classified. Because emulsifiers are active surface chemicals, they determine the electrical charge of the emulsion. In the preparation of emulsion bitumen, a small amount of this chemical is added to facilitate the formation of bitumen globules and stable suspension.
Most binders used in surface asphalts that use emulsions are cationic; This means that the bitumen particles in these emulsions have a positive charge. The positive ions that surround the bitumen particles in this emulsion stick to them in contact with the rock material and bind the bitumen particles to the material by forming an ionic bond. The initiation of bitumen absorption is the beginning of the failure of the emulsion, and with the onset of failure, the bitumen particles adhere to the material and become larger and larger. This process occurs faster with the density of materials or the use of accelerators.
Features of emulsion bitumen:
1. Possibility of transport to remote places in bulk (with bitumen tanker, truck and trailer) or barrel (preferably oil barrel).
2. Ability to use asphalt with low thicknesses.
3. High distribution speed of surface or thin asphalt and also, increase of asphalt operation due to drying less than 2 hours.
4. Suitable for any type of asphalt, foundation and pavement (street - highway - airport runway).
5. No need for heating during storage, transportation and spraying.
6. Can be used at ambient temperature (minimum temperature 5 و C and maximum 80 سل C) and on wet pavements.
7. Proper permeability due to high fluidity.
8. The complexity of the required machinery and ease of use.
9. Full compliance with the environment and non-pollution, both in the manufacturing process and in the transportation, spraying and refining process.
10. Rapid failure of emulsion bitumen in contrast to rock and air materials (only 1 to 2 hours).
11. Not toxic and odorless.
12. Inability to fire while holding, carrying and carrying.
13. Change the color from brown to black after completing the process of breaking the emulsion bitumen and preparing for traffic or the implementation of the next layer of asphalt.
14. Give indirect heat if the ambient temperature drops below 5 degrees Celsius, with a system such as hot oil piping to increase the temperature to 5 to 15 degrees to prevent freezing and duplication.
15. Staying in the tank for at least 3 months at the temperature specified in paragraph 6. The moon remains homogeneous and mixed).
16. Pump and discharge from the trailer tanker to the bottom of the tank and do not release the emulsion bitumen from a height of more than 100 cm (to keep in the tank, the emulsion bitumen must be pumped to the floor or the end of the source or with a hose to the end of the tank It is stored, pumped from the trailer tank to the storage tank. If it is released from above, it foams and doubles.
17. Crushing and washing of stone materials and not having soil (or 3-0 materials in aggregates) to the emulsion bitumen that sticks to the first object in its contact due to its high adhesion, instead of sticking to the soil on the materials, to The stone materials themselves should stick to the target and not be pellets or rolls (it is enough to spray the sitting stone materials with a sprinkler machine so that the soil or 3-0 materials sink into the side of the target stone materials and somehow free the stone materials from the soil. To achieve the highest level of adhesion between the emulsion bitumen and the stone materials and the desired penetration).
Soluble bitumen: Soluble
bitumen is obtained by dissolving bitumen in solvents or petroleum oils. The type and quality of soluble bitumen depends on the quality of the bitumen, the type of solvent and the amount of solvent. The higher the amount of petroleum solvents in the bitumen, the greater the psyche. Lack of access to bitumen heaters, high temperature decomposition of bitumen, cooling of bitumen during operation, inability to penetrate porous minerals, workers' safety, fire and time consuming causes that in some cases Use soluble bitumen. Solvent bitumens are used in road construction for surface coatings, permeability, surface asphalt, cold factory asphalt or mixed on-site use. Slow bitumen (MC) is prepared by dissolving pure bitumen in white oil, which is the suffix number representing bitumen viscosity in terms of centiostox.
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